The present invention relates to a storage system which is connected to a client and that stores the data that this client uses.
In recent years, storage systems called NAS (Network Attached Storage) that store data transferred from a client via a network have become widespread. An NAS consists mainly of a server device and a disk device. The server device receives commands relating to input and output of data from the client, and controls reading and writing of data to the disk device according to this command.
In recent years, as the performance of clients increases, the size of data handled by the clients has increased. Because of that, there is a desire for an increase in storage capacity for storage systems, as well as a desire for increased data input and output speed. Generally, to increase the input/output speed of data for a storage system, it is necessary, for example, to replace the server device CPU with a high performance item, or to increase the capacity of the built in memory, etc. However, since there is a limit to the types of CPU and memory capacity that can be incorporated into a server device, in recent years, there has been proposed technology that attempts to increase the performance of the overall system by increasing the number of server devices themselves.
In this way, as a storage system comprising a plurality of server devices, disclosed in U.S. Pat. No. 6,671,773 is the structure of a storage system for which a plurality of server devices called network elements are connected to a plurality of disk devices via a switching device.